The present invention relates to pharmaceutical compositions for oral administration comprising fenofibrate which enable improve dissolution and bioavailability.
Fenofibrate is practically insoluble in water. This causes fenofibrate to exhibit a low rate of dissolution in aqueous media (including gastrointestinal fluids), which results in inadequate bioavailability (absorption into systemic circulation) after oral ingestion.
In order to make a composition comprising fenofibrate that will enable maximum bioavailability, it is necessary to incorporate into the composition a feature that increases the rate of dissolution of the drug to enable it to dissolve in the gastrointestinal fluids.
Several ways of increasing the rate of dissolution of drugs having low solubility in water are known in the prior art.
One approach is micronization. In this approach, the drug is milled to fine particles, typically having a mean diameter of only a few microns. A second approach is to include a surfactant in the composition.
For the drug fenofibrate, neither micronization alone nor use of a surfactant alone enables maximum bioavailability. US Patent 4895726 discloses that the rate of dissolution and the bioavailability of fenofibrate can be maximized by co-micronization of fenofibrate. In this process the fenofibrate is first mixed with the surfactant and then the mixture is micronized.
A composition made according to the invention of U.S. Pat. No. 4895726 is sold in Canada as elsewhere under the tradename Lipidil Micro. The need for microcomposition and use of a surfactant adds to the cost of capsules containing fenofibrate.
In view of the limitations of the prior art, it is an object of the present invention to enable maximum bioavailability of fenofibrate without the need for micronization and without the need for use of a surfactant.
It has been found the rate of dissolution and the bioavailability of fenofibrate can be substantially improved by making a solid dispersion of a disintegrant in the fenofibrate. The solid dispersion can be made by heating and melting the fenofibrate, blending the disintegrant into the molten fenofibrate, and then cooling and solidifying the mixture.
Fenofibrate has a melting point of about 80xc2x0 C and can be melted without decomposition.
A disintegrant will be understood to be a substance which is hydrophilic and swells upon absorption of water. Disintegrants are used as excipients (inactive ingredients) in pharmaceutical tablets and capsules so that, when a tablet or capsule is ingested, the disintegrant will cause the tablet or capsule to absorb gastrointestinal fluid and, as a result, to swell and disintegrate, so as to release the active drug for dissolution and absorption.
The most commonly used disintegrant is starch.
Disintegrants with very high capacity to absorb water and swell are known as xe2x80x9csuper-disintegrantsxe2x80x9d, which include such substances as croscarmellose sodium, sodium starch glycolate and crospovidone.
As aforesaid, a solid dispersion comprising a disintegrant dispersed in the fenofibrate can be made by melting the fenofibrate, blending the disintegrant into the molten fenofibrate and then cooling and solidifying the mixture. The solid can then be ground into granules for further processing into tablets or capsules.
Because of the very intimate mixing achieved by mixing the disintegrant into the fenofibrate in the molten state, it follows that each granule or particle of the ground-up solid dispersion will be an approximately uniform mixture of fenofibrate and disintegrant.
The solid dispersion is thus intrinsically different from a mixture achieved simply by physical mixing of fenofibrate in solid form and disintegrant, because in a physical mix each particle remains either pure fenofibrate or pure disintegrant.
It will be understood that in the process of making a solid dispersion, within the scope of the present invention, ingredients other than the fenofibrate and disintegrant may be included in the molten blend and thus incorporated into the solid dispersion. Such other ingredients may include, for example, water-soluble or water-insoluble ingredients which serve as surfactant, diluent, or for other purposes.
Alternatively, other ingredients may be mixed with the granules of solid dispersion, and the mix so achieved may be further processed into tablets or capsules.
The invention will be further illustrated by the following example, which is intended to be illustrative but not limiting of the scope of the invention.